Field of the Invention
The present invention relates to methods for manufacturing liquid-discharge-head substrates.
Description of the Related Art
Liquid discharge apparatuses, such as ink-jet printing apparatuses, have liquid discharge heads. A liquid-discharge-head substrate used in a liquid discharge head is called a chip and has an energy-generating element, such as a heating resistor or a piezoelectric transducer. The liquid is supplied with energy by the energy-generating element so as to be discharged. In such a liquid-discharge-head substrate, a flow channel and a liquid chamber are formed on a substrate composed of, for example, silicon, and the energy-generating element is disposed within the liquid chamber. The energy-generating element is connected to a wiring layer on the substrate, and an end of the wiring layer serves as a pad. The pad is connected to an external power supply of the liquid-discharge-head substrate by, for example, bonding. The energy-generating element of the liquid-discharge-head substrate is driven by being supplied with electricity from outside the liquid-discharge-head substrate via the pad.
The pad is constituted of the wiring layer, which is composed of, for example, aluminum, and a bump section composed of, for example, gold. In the manufacturing process of the liquid-discharge-head substrate, an electrical inspection of a semiconductor integrated circuit is sometimes performed on the wiring layer of the pad by using a contact probe. In the electrical inspection, the contact probe is brought into contact with the wiring layer in a manner such as to scrape the surface thereof. In this case, an insulation film, such as a natural oxidized film, and the wiring layer composed of, for example, aluminum are scraped by the contact probe, thus causing an electrical inspection mark having a protruding shape to form in the wiring layer of the pad. Although a cleaning process is subsequently performed, the electrical inspection mark having the protruding shape still remains in the pad. For example, when depositing an organic material onto the substrate, the electrical inspection mark may possibly cause the thickness of the organic layer to become uneven. Unless the electrical inspection mark is completely covered by a barrier metal layer to be formed in a subsequent step, alloying may occur between the wiring layer (e.g., aluminum) and the bump section (e.g., gold) to be laminated via the barrier metal layer, possibly deteriorating an electrode function.
Japanese Patent Laid-Open No. 2010-221656 discusses how the occurrence of an electrical inspection mark in the wiring layer of the pad is reduced by forming a plurality of steps in a region with which the contact probe comes into contact and by using the plurality of steps as a stopper layer.
In the method discussed in Japanese Patent Laid-Open No. 2010-221656, the occurrence of electrical inspection marks may sometimes be reduced. However, according to examinations conducted by the present inventors, the stopper layer may sometimes break if a large contact force is applied from the contact probe during the electrical inspection or if the stylus force applied to a first contact probe is large due to uneven lengths of a plurality of contact probes. As a result, a protruding structure (i.e., an electrical inspection mark) may form in the wiring layer.
The conditions for determining the size of an electrical inspection mark include the conditions of an inspection device. However, if the contact conditions of the contact probe that scrapes the insulation film are set so as to reduce the occurrence of electrical inspection marks, the insulation film may sometimes remain without being scraped, possibly resulting in uneven resistance values.